This invention relates to a pressure modulator and more particularly to a regulator for controlling the hydraulic pressure within a chamber.
Regulators for proportionally controlling hydraulic pressure in a chamber are widely used and, in one type of design, include a circular orifice having a ball disposed at one side thereof for orifice closure when the ball engages a seat formed in one side of the orifice structure. A solenoid actuated pin is positioned on the second side of the orifice and has a nose member which extends therethrough and is arranged to controllably open the orifice passage by unseating the ball in response to voltage signals of varying magnitudes which may be applied to the solenoid. The orifice passage is in fluid communication with a chamber in which pressure is to be controlled. As voltages of increasing magnitude are applied to the solenoid, the plunger advances to unseat the ball by an increasing amount thereby providing a progressively enlarging flow area for metering fluid flow into or out of the chamber to control the pressure therein.
An adaptation of this arrangement includes a solenoid-positioned plunger having a tapered nose member configured for fluid sealing engagement with the orifice when the plunger is in a first position. As voltages of increasing magnitude are applied to the solenoid, the plunger disengages the orifice seat to form a flow passage of increasing area, thereby permitting the controlled flow of fluid from the chamber and a consequent reduction of pressure therein.
Although these prior devices have heretofore provided a satisfactory means for regulating the hydraulic pressure within a chamber, both are subject to undesirable deformation of orifice seating surfaces over extended periods of service. Additionally, it has been found that the repetitive surface-to-surface contact of mating metal pieces tends to cause surface work hardening and resultant undesirable loss of small metal particles from the working surfaces, thereby impairing their effectiveness and contaminating the hydraulic system. Examples of prior art devices of this type are shown in U.S. Pat. No. 4,126,293 of Zeuner and U.S. Pat. No. 2,853,976 of Gerwig.
Other regulators for controlling the hydraulic pressure within a chamber include a proportionally positionable metering spool in closely fitted, sliding engagement with a spool bore. Positioning of the spool is by the application of voltages of varying magnitude to an associated solenoid for controllably opening a flow passage between a chamber and a tank. While this approach avoids the deformation of mechanical parts often associated with devices of the aforementioned type, the spool-type of pressure regulator has been found to be relatively sensitive to system contaminants and are frequently subject to silting caused by the accumulation of minute particles upon the bore-engaging edges of the spool. Additionally, designs of this type tend to have static and dynamic friction forces which are dramatically different from one another and tend to impair the accuracy with which the spool position may be controlled. All of the aforementioned design approaches are dependent upon accurate regulation of the magnitude of the voltage applied to the actuating solenoid. Unless this voltage is carefully regulated, impaired performance may result. Accordingly, a pressure regulator which is responsive to pulse width modulated electrical signals and which regulates pressure by means having no mechanical contact one with the other would be a significant advance over the prior art.